BOOK IX. 367 
Then twelve short posts are erected, whose lower ends are mortised into 
the sill that is near the back of the furnace wall; these posts are two feet 
high, exclusive of the tenons, and are three palms and the same number of 
digits wide, and two palms thick. A slot one and a half palms wide is cut 
through them, beginning two palms from the bottom and extending for a 
height of three palms. All the posts are not placed at the same intervals, the 
first being at a distance of three feet five digits from the second, and likewise 
the third from the fourth, but the second is two feet one palm and three 
digits from the third; the intervals between the other posts are arranged in 
the same manner, equal and unequal, of which each four pertain to two 
furnaces. The upper ends of these posts are mortised into a transverse 
beam which is twelve feet, two palms, and three digits long, and projects 
five digits beyond the first post and to the same distance beyond the fourth; 
it is two palms and the same number of digits wide, and two palms thick. 
Since each separate transverse beam supports four bellows, it is necessary to 
have three of them. 
Behind the twelve short posts the same number of higher posts are 
erected, of which each has the middle part of the lower end cut out, so that 
its two resulting lower ends are mortised into the back sill; these posts, 
exclusive of the tenons, are twelve feet and two palms high, and are five palms 
wide and two palms thick. They are cut out from the bottom upward, the 
slot being four feet and five digits high and six digits wide. The upper ends of 
these posts are mortised into a long beam imposed upon them; this long 
beam is placed close under the timbers which extend from the wall at the 
back of the furnace to the first long wall; the beam is three palms wide 
and two palms thick, and forty-three feet long. If such a long one is 
not at hand, two or three may be substituted for it, which when joined together 
make up that length. These higher posts are not placed at equal distances, 
but the first is at a distance of two feet three palms one digit from the second, 
and the third is at the same distance from the fourth; while the second is at a 
distance of one foot three palms and the same number of digits from the 
third, and in the same manner the rest of the posts are arranged at equal 
and unequal intervals. Moreover, there is in every post, where it faces the 
shorter post, a mortise at a foot and a digit above the slot; in these mortises 
of the four posts is tenoned a timber which itself has four mortises. Tenons 
are enclosed in mortises in order that they may be better joined, and they 
are transfixed with wooden pins. This timber is thirteen feet three palms 
one digit long, and it projects beyond the first post a distance of two palms 
and two digits, and to the same number of palms and digits beyond the 
fourth post. It is two palms and as many digits wide, and also two palms 
thick. As there are twelve posts it is necessary to have three timbers of this 
kind. 
On each of these timbers, and on each of the cross-beams which are laid 
upon the shorter posts, are placed four planks, each nine feet long, two palms 
three digits wide, and two palms one digit thick. The first plank is five feet 
one palm one digit distant from the second, at the front as well as at the back, 
